add --python to specify python version

[luisdavim]

it would be nice to be able to do:

pipsi --python=python2.7 install foo

[sanyer]

but you can already do this

[benwbooth]

@sanyer how?

[benwbooth]

@sanyer nevermind figured it out

[benwbooth]

e.g.

pipsi install --python python3.6 <package>

[sanyer]

$ pipsi install --help

Usage: pipsi install [OPTIONS] PACKAGE
    ...
Options:
    --python TEXT           The python interpreter to use.
    ...

[tedmiston]

I ended up here through Google looking for something like:

$ pipsi upgrade --python python37 ipython

My goal was to upgrade the python version of my existing ipython virtual environment from 3.6 to 3.7. It would be cool if we supported this use case.

For now, I ended up just uninstalling and doing a fresh install on the new Python version.

[00willo]

FYI, works with pyenv nicely too.

pipsi install --python $PYENV_ROOT/versions/3.6.6/bin/python molecule